It has long been recognized that the quality of foods can be maintained for extended periods of time if they may be stored in an environment having reduced concentrations of oxygen. Meats are especially affected by oxygen, and meat items such as luncheon meats are extremely perishable in an atmosphere containing oxygen. In the presence of oxygen the food item, particularly meats, loses flavor and tends to spoil due to the growth of yeast, molds and some bacteria that develop rapidly in the presence of oxygen even during refrigerated storage. It is known that the volume of oxygen about the food may be reduced by enclosing the food unit in film having low oxygen permeability and sealing while under a vacuum. If the food unit is placed in a chamber, a vacuum of 29 inches mercury drawn on the chamber and the film sealed about the unit when it is under vacuum, a package may be obtained having a vacuum of about 24 to 26 inches mercury, but the concentration of oxygen within the package remains at about 20%. For example, in a 2-ounce package of bologna ( 2 slices) 0.47 to 0.99 cc of air having an oxygen concentration of 20% is left in the package apart from what may be in the meat body itself. This amounts to 0.094 to 0.198 cc of oxygen. The oxygen is also entrapped within the meat. In the example of the 2-ounce bologna package, the meat itself contains 0.16 to 0.33 cc of entrapped and absorbed air, which computes to 0.032 to 0.066 cc of oxygen. This comes to a total of 0.125 to 0.264 cc of oxygen still contained within the typical vacuumized package previously known in the art. Such a package is known to have a shelf life, under ordinary marketing conditions, of from 30 to 60 days.
We have sought to discover processes for packing units of food in a film enclosure in which the volume and concentration of oxygen within the package and in the food unit is substantially reduced from that of the prior practice as above explained and which will result in packages which have a much longer shelf life. This discovery and other objects and advantages of my invention will become apparent as this specification proceeds.